Since age 18, Zechariah Manyok Biar fought in the revolutionary army that won South Sudan’s independence from Sudan in July 2011. But now the 28-year-old is in exile from the country he helped liberate.

The huge Russian-made helicopter descended slowly towards conical mud huts clustered together and surrounded by endless grassland, lush and green with the season’s rains here in the South Sudanese village of Yuai.

South Sudanese soldiers are allegedly beating and torturing civilians in the midst of a disarmament campaign in Jonglei state, and many have been unable to access justice because of a lack of prosecutors and judges, according to the United Nations and Human Rights Watch.

The streets have been swept clean and lined with flags to mark the first anniversary of South Sudan’s independence. But cosmetic changes in the capital, Juba, mask deep concerns about the future of the world’s newest nation.

Civil society groups are calling on the United Nations peacekeeping mission to withdraw support from a disarmament programme they say could spark further violence in South Sudan’s volatile Jonglei state.

Hamid Yussef Bashir said he walked for 17 days with his wife and five children to get to a refugee camp in South Sudan. Here in Jamam, they joined about 37,000 other people who fled from the war across the border in Sudan’s Blue Nile state.

As Sudan and South Sudan meet for the latest round of negotiations featuring oil as a key issue this week, four ships loaded by Khartoum with southern crude are carrying their disputed cargoes to unknown buyers.

In the ward of a partially destroyed clinic, Mangiro (who did not give his last name) sat on a bed next to his wounded nine-year-old daughter, Ngathin. The little girl is fortunate, she survived the recent inter-ethnic clashes in Pibor county that killed her mother and sisters.

In the sprawling settlement of Yida, just south of the Sudan border, more than 20,000 people have gathered after fleeing battles in the country's Southern Kordofan state. But they now find themselves caught up in a new conflict, as recent clashes along the frontier have some warning of the possibility of war.

Joyous reunions accompanied the latest batch of South Sudanese returning from Sudan to their newly independent homeland. But the returnees will face huge challenges integrating into South Sudan, which became the world's newest nation on Jul. 9, but also one of the poorest.